The Star Tribune had stretched its rules of inclusion the past couple of years to ensure that we had enough Minnesota-based public companies to have 100 companies on the Star Tribune 100.

This year, the rules tightened, ensuring a list that wouldn't fill 100 spots.

There is precedent: The Big Ten includes 14 colleges and universities. The Wilshire 5000 Total Market index, a popular index that measures the performance of all U.S. equity securities, had only 3,818 members as of Sept. 30. Membership in that index has ranged in number from 3,069 to 7,562.

What didn't change was a general rule that lists a company whose management headquarters is in Minnesota, even if it is officially based in another country. We couldn't ignore the likes of Medtronic PLC (Fridley and Ireland), Pentair PLC (Golden Valley and United Kingdom) and Stratasys Ltd. (Eden Prairie and Israel). We even briefly added Ridley Inc. (Mankato and Winnipeg, Manitoba) this year for similar reasons.

Ridley is an animal nutrition company that was founded in 1994. It had acquired Mankato-based Hubbard Feeds in 1997, and its management headquarters is in Mankato. The company was officially registered in Canada, and its shares traded on the Toronto stock exchange. Almost as soon as we decided to add Ridley to the list, the company announced it was being acquired by a subsidiary of privately held Alltech Inc. for approximately $428 million. The acquisition of Ridley will help Alltech, an animal feed company based in Nicholasville, Ky., reach its goal of $4 billion in global sales in the next few years.

OTC stocks

The biggest change was eliminating companies whose stock trades on over-the-counter (OTC) exchanges. Some of those companies trade sporadically or may file infrequently with the Securities and Exchange Commission. Some of those companies do have significant revenue and are larger than some companies at the bottom of the Star Tribune 100. For example, casual restaurant chain Granite City Food & Brewery Ltd. had $130 million in annual sales for 2014 but in April 2013 was delisted and in December deregistered as a public company.

Also, public shell companies looking for an operating company in which to invest were not included.

IPO adds

Minnesota loses more public companies each year than it creates via initial public offerings.

Two Minnesota companies completed initial public offerings in the last 12 months. Making its debut on the Star Tribune 100 as No. 70 is Plymouth-based Entellus Medical, which went public on Jan. 28 at $17 per share, raising $78.3 million.

Minneapolis-based GWG Holdings raised $10 million from an IPO it completed on Sept. 25. The company provides financial solutions for customers looking to monetize the actuarial value of life insurance policies in the secondary market. GWG debuted at No. 74.

Chanhassen-based Cachet Financial completed an IPO on July 9 and has $2.6 million in annual revenue, but its shares opened trading on the OTC Bulletin Board, so it is not on the list.

OTC to major exchange

Last year, Dakota Plains Holdings did not have high enough sales to make the list and also was an OTC stock. On June 14, the Wayzata-based provider of rail services to oil and frac sand companies moved up to the New York Stock Exchange and is No. 77 on the list this year.

Craig McKenzie, CEO of Dakota Plains, said in the company's news release announcing the move to the NYSE: "Stepping up to a national exchange will heighten our profile in the capital markets and give us an important opportunity to broaden our stockholder base and increase daily trading liquidity."

Mergers and acquisitions

Corporate mergers continue to be the biggest cause of companies dropping off the list. Enventis (55th in 2014), formerly known as Hickory Tech Corp., merged with Consolidated Communications Holdings Inc. on Oct. 8.

XRS Corp. (71st in 2014) of Eden Prairie on Nov. 3 was taken over by Omnitracs, a private-equity-owned company that is building a suite of products and services for fleet management.

The trend could continue.

Digital River's (47th in 2014) $840 million acquisition by an investor group led by Siris Capital Group finalized on Feb. 12, 2015.

Life Time Fitness is still on the list this year, but the company announced on March 16 that it would be acquired by private equity investors for $72.10 per share, or more than $4 billion. That deal is on schedule to close in the third quarter of this year.

Pioneer Power Solutions acquired Eden Prairie-based Titan Energy Worldwide (88th last year) on Dec. 31, 2014.

Bankruptcy

Victoria-based HEI Inc., with annual revenue of $45 million, was ranked 75th last year. However, besides being an OTC stock, the company filed for Chapter 11 bankruptcy protection in January.

Moves

Creative Realities, formerly known as Wireless Ronin Technologies, was ranked 95th last year. Besides also being an OTC stock, the company moved its headquarters to New York.

Beneficiaries

Sunshine Heart and Enteromedics were the biggest beneficiaries of the new OTC rule. Both are early-stage medical device companies with limited or no revenue, but are nonetheless traded on major exchanges. Neither was ranked in the top 100 last year but they took the last two spots — 89 and 90 — on this year's list.